This invention relates to the field of scene simulators for target seekers and has special applicability to millimeter wave radar target seekers.
One purpose of radar scene simulators is to help test target seeking radars, especially those used in missiles. Due to the complexity and high cost of missiles, it has become too expensive to test-fire missiles to determine whether their target seekers are operating properly. Besides the great cost of such testing, test-firing makes it difficult to analyze a missle target seeker which failed.
Radar scene simulators were designed to test whether radars respond as designed to specific scenes. Early scene simulators used only a corner reflector situated in the radar field of view. The corner reflector reflected transmitted signals back to the target seeker and was helpful in determining only whether the target seeking radar was receiving reflections of the signals it transmitted.
Another method of testing target seeking radars uses a radar transponder in the target seeker's field-of-view which transmits to the missile signals designed to simulate the signals which would be reflected from a known target. Because such transmitting radars are not synchronized with the target seeker, a small difference in frequency between the transmitting radar and the target seeker signals could cause a correctly functioning radar to respond incorrectly.
FIG. 1 shows a more elaborate system for radar scene simulation. A target seeker (not shown) transmits its radar signal at frequency f.sub.s to an array 100 of RF transceiver antennae. Antenna array 100 includes a plurality of antenna triads. The use of an array of antenna triads is explained in U.S. Pat. No. 4,467,327, filed on Sept. 22, 1981 and issued on Aug. 21, 1984, which is incorporated herein by reference.
Each transceiver antenna receives the target seeker radar signal. The signals from an antenna triad are placed on whichever of lines 110.sub.1 -110.sub.z that correspond to that triad and sent through switch matrix 110 into signal generator 120. Switch matrix 110 switches the signals from a selected antenna triad onto lines 121-123 and to signal generator 120.
Signal generator 120 forms signals to create the desired radar scenes for the target seekers by mixing the received signals, R.sub.s, with target signals, T.sub.s. Signal generator 120 gives this mixed signal, denoted as R.sub.s +T.sub.s, the proper amplitude and sends it to a selected antenna triad via switch matrix 110 and the lines 110.sub.1 -110.sub.z which correspond to that triad.
Data processor 130 controls signal generator 120 to create the target signals Ts and controls switch matrix 110 to ensure the correct routing of signals.
The system in FIG. 1 is adequate for CW target seekers operating in the radio frequency range because transmission lines 110.sub.1 -110.sub.z can be coaxial cables. For target seekers operating at millimeter wave frequencies, however, transmission lines 110.sub.1 -1l0.sub.z must be mechanical waveguides. Such waveguides are bulky, difficult to maintain, and very expensive.
An object of this invention to create low cost scene simulator systems for millimeter wave target seekers.
A further object of this invention is to create scene simulators which have a great deal of flexibility and will allow complete testing of both CW and pulse target seeker radars.
Additional objects and advantages of this invention will be set forth in part in the description which follows and in part will be obvious from that description or may be learned by practice of the invention. The objects and advantages of this invention may be realized and obtained by the methods and apparatus particularly pointed out in the appended claims.